Side-channel blowers or pumps have previously been described. In a vehicle, they serve, for example, to convey fuel, to blow secondary air into the exhaust system, or to convey hydrogen for PEM fuel cell systems. The drive is usually effected by an electric motor whose output shaft has the impeller arranged thereon. Side-channel blowers have previously been described in which only one flow channel is formed on an axial side of the impeller in a housing part, as well as side-channel blowers formed with a flow channel on either axial side of the impeller, in which case both flow channels are in fluid communication with each other. In such a side-channel blower, one of the flow channels is most often formed in a housing part which serves as a cover, while the other flow channel is formed in the housing part to which the drive unit is typically mounted, on the shaft of which the impeller is arranged to rotate therewith. The impeller is designed at its periphery so that it forms one or two circumferential vortex ducts together with the flow channel or the flow channels surrounding the impeller.
In side-channel blowers with two axially opposite vortex ducts, the impeller blades are divided axially across a radial section into two sections which are respectively assigned to the opposite flow channel. Pockets are formed between the impeller blades in which, when the impeller rotates, the fluid conveyed is accelerated by the impeller blades in the circumferential direction as well as in the radial direction so that a circulating vortex flow is generated in the flow channel. With impeller blades of a radially open design, an overflow from one flow channel to the other most often occurs via the gap between the radial end of the impeller and the radially opposite housing wall.
In order to obtain the best possible conveyance or pressure increase, different measures have been taken in conveying gases and liquids which are due to the different behavior of compressible and incompressible or slightly compressible media when they are conveyed.
The generation of noise should also be taken into account when conveying in side-channel blowers since acoustically disturbing pressure surges occur at the beginning of the interruption zone immediately after a medium has flowed over each impeller blade because compressed gas is still present in the pockets between the impeller blades, which gas has not been completely expelled via the outlet and is suddenly accelerated against the walls of the interruption zone when it reaches that zone. This causes significantly increased noise emissions.
Various outlet contours and designs of the interruption zone have previously been described for this reason. For example, DE 10 2010 946 870 A1 describes a side-channel blower in which recesses are formed behind the outlet in the radially delimiting housing wall which extend in the circumferential direction for several times the distance between the blades so that the interruption zone is formed in a stepped manner at the housing wall. The generation of noise may well be improved thereby, however, with such a design, the interruption zone extends over a circumferential angle of more than 60°, whereby the possible delivery rate and thus the efficiency of the blower is decreased since a shorter path is available for increasing pressure. The radial interrupting gap for preventing a short-circuit flow from the outlet directly to the inlet via the interruption zone is also merely about 0.3 mm. As a consequence, if such a blower is used in internal combustion engines at outside temperatures below the freezing point, condensates in the gap may freeze and block the impeller. Very accurate tolerances must further be observed during production and assembly so as to prevent contact between the impeller and the housing wall.
A side-channel pump is also described in DE 691 01 249 T2 whose interruption zone is significantly shortened. To still prevent an overflow and to minimize noise generation, various measures are taken, which, however, are based on the assumption that an overflow occurs in the region of the closed disc of the impeller. To avoid an overflowing of the interruption zone, the radial gap between the impeller and the housing wall is kept as small as possible, whereby problems in manufacture are again caused due to tolerances that must be observed, and a significant generation of noise occurs in the interruption zone as the gas leaves the impeller in the radial direction.